A new theory is introduced and advanced in this paper. It saysthat radial force affects to fluid flow in rotating axial flowpassage at whole flow rate, including maximum efficiencypoint, and the velocity distribution shifts outer radius. That is,axial mass flow rate and axial component of velocity, consideredon the developed cylindrical surface, increase at outside tipdiameter and decrease at inside hub diameter. These tendencybecome stronger with the decrease of the flow rate and with theimprovement of pump efficiency. By applying this new concept,the mechanism of downstream backflows occurrence and itsinterrelation with pump efficiency among axial flow pumps areinvestigated. All the results obtained show very good agreementwith experimental test results. And, it is concluded thatapplication of aerofoil theory to axial flow pump is incorrect asits basic concept is quite opposed to this new theory.
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